A block brake actuator, normally a so called brake unit containing a brake cylinder and a slack adjuster, can conventionally be provided with a brake block holder suspended therefrom. The suspension by hangers or links is such that the brake block holder (provided with a brake block) can move in the plane of the actuator push rod to and fro braking engagement with a wheel to be braked.
When the brake actuator is fixedly mounted in the vicinity of the wheel to be braked, only very limited axial movements of the wheel or wheel-set can be allowed.
In recent years there has been a clear tendency towards rail vehicle designs allowing greater axial movements of the wheel-sets. Certain ways of solving the problem with braking an axially movable wheel-set are known. Especially, when as preferred the brake actuator is fixedly mounted in the rail vehicle under-frame or bogie in the vicinity of the wheel to be braked, a solution with leaf springs to suspend the brake block holder as set out above is known. Such a prior art solution, on which the present invention is based, is shown in U.S. Pat. No. 4,630,714; reference is made to this prior art.
In this prior design, which per se was a successful break-through with extended commercial use, the brake block holder is suspended at its center by a stack of leaf springs at each side. The upper connection to the actuator bracket is only rotational, whereas the lower connection to the brake block holder center is rotational and pivotal to allow the brake block holder to remain vertical (for braking co-operation with a wheel tread) in spite of deflection of the hangers in the form of the leaf springs. Although it does not really appear from said publication, the design for obtaining this rotational and pivotal connection is quite complex. It has to be very well protected, because intrusion of moist and dirt to its intricate parts (for example spherical bearings) has to be avoided.